Apparatus for the production in a converter of steel which may have a high carbon content



Oct. 30, 1962 H. NEUHAUS ETAL 3,061,299

APPARATUS FOR THE PRODUCTION IN A CONVERTER OF STEEL WHICH MAY HAVE A HIGH CARBON CONTENT Filed Oct. 7, 1958 FIG. 1

3,061,299 APPARATUS FOR THE PRQDUCTIQN IN A CON- VERTER F STEEL WHICH MAY HAVE A HIGH CARBUN CONTENT Herbert N euhaus, Swolinsikystrasse, Johannes Kosmider, 37 Hesterstrasse, and Otto Arthu r Weyel, 18 an der Hutte, all ofHagem-Haspe, Germany Filed Oct. 7, 1953, Ser. No. 765,784 Claims priority, application Germany Oct. 9, 1957 1 Claim. (Cl. 266-36) This invention relates to a process for the production of steel from phosphorus-containing pig-iron in a converter.

It provides a process which makes it possible to prepare directly from such pig-iron, steel, which may if desired also be of high carbon content, i.e. in one operation in a converter exclusively by low carbonisation i.e. avoiding the step of recarburising the steel to the desired end carbon content after finishing the refining process which is otherwise necessary in such cases.

The usual operation of subsequent recarburisation after the refining for the purpose of preparing high carburised steels is necessary in the working up of pigiron with comparatively high phosphorus content in the known process, because with such pig-iron, for metallurgical reasons, the burning of the phosphorus can only take place after the decarburisation is finished. A tap of the melt according to the desired end carbon content is only possible in refining pig-iron of low phosphorus content according to the overhead blast principle. Even then, however, on account of the small duration of the entire blast process and the high velocity with which the decarburisation proceeds, there is no satisfactory certainty of result with regard to the end carbon content attained.

It has already been proposed to obviate these difficulties by a manner of operation in the refining process which results in a preliminary delay of the course of the dephosphorisation and moreover a retardation of the velocity of the carbon combustion and thereby makes it possible to break off the refining process at an accurately defined carbon content.

One of the know processes of this kind which is especially advantageous with regard to its certainty of result,

consists in carrying out, in refining with oxygen or air enriched with oxygen, the blowing of the refining gases onto or into a primarily formed lime slag containing FeO, after the slag formation, while avoiding direct contact of the blast agent and metal, whereby the reaction process thus proceeds Within the body of the slag and the phosphorus can be slagged by indirect oxidation until only traces are left, although the residual carbon content of the bath still amounts to up to 1.5%.

This known process further also avoids-with the exception of its initial phase during which the layer of slag is formedthe occurrence of undesired brown fumes of iron, and the iron losses associated therewith. Its practicability in use however is limited to the production of steels with up to medium carbon contents. By the invention this known process is modified in such a way that a preparation of steels with any desired end carbon content of the finished steel, which comes into question in practice, is made possible with complete certainty of result with regard to the said carbon content.

This is achieved according to the invention in that when carrying out the dephosphorisation process according to the known method indirectly above the slag by blowing a blast agent with a high oxygen content onto the surface of the layer of slag, the decarburisation phase is carried out while at least partially blowing through the bed according to the bottom blast principle. The possibility of this separation from each other of the depho-sphorisa- Patented Oct. 30, 1962 tion and the decarburisation, which are carried out in direct succession, i.e. in one operation, is provided according to a special feature of the invention, in that the dephosphorisation takes place by means of oxygen or refining gas of high oxygen content blown onto or into the layer of slag in the horizontal position of the converter, whereupon the decarburisation takes place by blasts, preferably with refining gas containing less oxygen, at least partly through the bath, i.e. through the bottom tuyers of the converter.

In order to make possible this method of operation, according to the preferred embodiment of the new process, after the dephosphorisation is finished, after which a strongly foaming slag of high iron content is present on the bath surface and which remains in the converter, the converter is brought into a more or less strongly inclined position as a result of which a smaller or larger number of the blast tuyeres arranged in the bottom of the converter are submerged beneath the surface of the bath and blow through the bath. By a more or less strong inclination of the converter, the number of submerged tuyeres can be varied and consequently the decarburisation speed can be extensively controlled.

In order to prevent the occurrence of brown iron fumes also in the initial phase of the formation of the layer of slag, according to a further feature of the invention, the slag-forming phase (which is limited by the time interval of the slagging of the silica contained in the pig-iron by the slag-forming compounds) can be carried out separately from the following dephosphorisation phase in the upright position of the converter, i.e., with bottom tuyeres, whereby care must be taken however that in this initial phase a carbon combustion is practically avoided. This is achieved in that the blowing takes place in this phase with blast gases of the smallest possible oxygen content or those which yield only a little oxygen also by their dissociation. This initial phase up to the formation of the layer of slag takes about 2 to 3 minutes.

A tiltable converter suitable for carrying out this process is shown in the accompanying drawing in which FEGURE l is a section through the converter in full lines in horizontal position, i.e. during the depho-sphorisation process, and in dotted lines in vertical position, i.e. during the decarburisation, and

FIGURE 2 is a section on the line AB of FIGURE 1.

As may be seen from the drawing, the converter has in the usual manner normal buttom tuyeres b with a wind-box a which is connected to a source of refining gas substantially higher than the refining gas flowing through the bottom tuyeres b and in the horizontal position of the converter is situated at one side of the same.

At the back, and/or if desired also at the sides, of the converter there are arranged further Wind-boxes c or c from which is led refining gas of high oxygen content through blast tuyeres connected thereto during the dephosphorisation carried out in horizontal position of the converter, onto or in preferably sloping direction over the surface of the bath.

The arrangement of the bottom tuyeres is thus the same as in the case of a normal bottom-blasting converter with the single exception that the total tuyere crosssection may be about 20 to 30% less.

The tuyeres blowing from above consist of tubes d of copper led through the refractory lining of the converter, which are rammed down or embedded in the dolomite mixture forming the lining during the renewal of the converter. The arrangement of these copper tubes is preferably such that the refining gas of high oxygen content can come into reaction with the metal surface or the layer of slag with the smallest possible losses. They are, as may be seen from FIGURE 1, mounted substantially in the middle portion of the rear of the converter or the sides and in the case of a converter of normal dimensions are arranged at distances of the order of magnitude of at least 1500 mm. from the mouth of the converter and 800 mm. from the bottom. The lateral blast tuyeres are arranged so that they act in an inclined direction or nearly tangentially on the surface of the bath.

In the horizontal position of the converter, i.e. during the dephosphorisation process, the whole of the bottom tuyeres lies above the bath. It will be immedia ely apparent that by tilting the converter into a more or less greatly inclined position, a larger or smaller number of blast tuyeres [2, depending on the intended result of the decarburisation process, dip into the bath and blow therethrough, whereas the tuyeres which do not dip into the bath blow like a fan onto the bath so that in this phase all possible variations are provided between exclusive blowing through the bath and partial blowing onto the bath.

We claim:

A converter for the production of steel of any desired carbon content from a phosphorus-containing pig iron, comprising a tiltable, vertical, cylindrical vessel for confining a molten metal bath, tiltable mounting means for said vessel, a first set of tuyeres disposed normally through and along substantially the entire bottom of said vessel for blowing a refining gas of normal oxygen content through said bath while said vessel is in a vertical position and alternatively partially through said bath and partially onto the surface of said bath when said vessel is in a tilted position, means for supplying a refining gas of normal oxygen content to said first set of tuyeres, second sets of tuyeres diametrically opposed along the cylindrical wall of said vessel and disposed through said well at an angle to the radius for blowing a refining gas of high oxygen content angularly onto the surface of said bath when said vessel is in a tilted position, a third set of tuyeres disposed diametrically along and normally through said cylindrical wall of said vessel and located between said second sets of tuyeres for blowing a refining gas of high oxygen content substantially vertically onto the surface of said bath when said vessel is in a horizontal position, and means for supplying a refining gas of high oxygen content to said second and third sets of tuyeres.

References Cited in the file of this patent UNITED STATES PATENTS 286,067 Reese Oct. 2, 1883 741,505 Kirk Oct. 13, 1903 757,803 Burrow -a Apr. 19, 1904 1,140,550 Weissenburger May 25, 1915 1,318,906 Nielsen Oct. 14, 1919 1,352,580 Cinille Sept. 14, 1920 1,711,738 Madorslty May 7, 1929 2,333,654 Lellep Nov. 9, 1943 2,599,158 Brasscrt June 3, 1952 2,641,461 Lewis June 9, 1953 2,733,141 Sims Jan. 31, 1956 2,789,046 Speith et al. Apr. 16, 1957 

